f(x)=–3x3–1x2+1x+1Find the average slope of this function on the interval (–2–1).
By the Mean Value Theorem, we know there exists a c in the open interval (–2–1) such that f(c) is equal to this mean slope. Find the value of c in the interval which works

I found the mean which is -17 but I can't get the C. I don't know what im doing wrong